This is a great question. From a purely philosophic perspective, I would agree that you would want a speaker that has a perfectly flat frequency response from 20hz to 20khz and compare deviations in terms of sound profile. If everyone had this as a baseline and new what this sounded like, reviews would be exponentially more valuable.
However, even if you found this speaker, it would most likely not behave that way in your room. Your choice in amplification and source is going to alter its sound profile. And finally, it may not be to your liking. Just because something is conceptually ideal, doesn't mean it is your preference. Additionally, wouldn't use a speaker of that sort to evaluate a 300B SET.
Philosophically, I get it. In practice, it might be better to choose a speaker in every BestBuy as your "reference" so that people have a common, mainstream point of comparison.
However, even if you found this speaker, it would most likely not behave that way in your room. Your choice in amplification and source is going to alter its sound profile. And finally, it may not be to your liking. Just because something is conceptually ideal, doesn't mean it is your preference. Additionally, wouldn't use a speaker of that sort to evaluate a 300B SET.
Philosophically, I get it. In practice, it might be better to choose a speaker in every BestBuy as your "reference" so that people have a common, mainstream point of comparison.